Low permeability formations generally require significant stimulation to develop well productivity large enough to be of commercial value. Hydraulic fracturing, using proppant laden slurries and/or acid, is most commonly used in these stimulation applications. While individual well productivity usually is enough to generate profitable results, effective recovery of a significant percentage of the hydrocarbon in place is not assured. For example, in the Annona Chalk formation of the Caddo Pine Island Field in northwestern Louisiana, hydraulic fracturing has been utilized as a part of the initial completion procedure in most wells. While this results in acceptable profitability for most wells, the projected cumulative recovery for the field is only about 15% of the original-oil-in-place (OOIP).
One method for increasing the percentage recovery is to reduce spacing between wells which, when considering that each well is fractured, is tantamount to reducing the distance between fractures. Another method for decreasing the distance between fractures is described in Strubhar et al. U.S. Pat. No. 3,835,928 issued. Disclosed therein is a method for drilling a deviated wellbore in a direction substantially normal to the preferred induced fracture orientation and then creating multiple vertical fractures from the deviated wellbore. This was accomplished by selecting individual locations along the wellbore and alternately perforating and treating each set of perforations individually. The normal practice in deviated wellbores is to perforate with a high shot density to create a single, vertical fracture.
Medlin et al. in U.S. Pat. No. 4,415,035 disclose a method for forming fractures in a plurality of vertically disposed hydrocarbon-bearing formations communicating with a well equipped with a casing penetrating a subterranean earth formation. It is applicable to those hydrocarbon-bearing formations penetrated by said cased well that have exhibited at least a predetermined minimum pressure increase during previous individual fracturing treatments in other nearby production wells in the areas identified. Perforations are formed in the well casing at the locations of such identified hydrocarbon-bearing formations. Hydraulic pressure is then applied through the perforations to the plurality of hydrocarbon-bearing formations simultaneously, whereby each formation is fractured in proportion to the pressure increase in such formation during the application of hydraulic pressure.
Although pressure was applied through the perforations to the plurality of hydrocarbon-bearing formations simultaneously, fracturing occured in each formation sequentially. Also, in order for the method to work, each formation must have exhibited at least a predetermined minimum pressure increase.
Therefore, what is needed is a method to create simultaneously, multiple vertical fractures in a deviated wellbore located in a subterranean formation or reservoir where the formation is not required to exhibit a predetermined minimum pressure increase.